Bob KowalskiImperial College London
with Jacinto Davilaand Miguel Calejo
with support from
D2 Legal Technology, LondonAora, LondonLodgeIT, Perth
with contributions from
Veselin KaradotchevZiyan Fu
Logical English for legal applications
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What is Logical English (LE)?
Historical development of LE
Examples of LE
Lessons Learned and Prospects for the Future
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● expert systems● computable and smart contracts● rules as code● plain English laws
Legal applications of LE
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Basic Logical English (LE) ● syntactic sugar for logic programs (pure Prolog):
conclusion if conditions forminfix predicatesimplicit quantification of variableshigher-order (or meta? or modal?) predicates.
● readable without training in mathematics, computing or logic.
● unambiguous:no pronouns (he, she, it, they)one word = one meaningno inflectiontime, but no tenseno lexicon.
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extensible
Relationships with other work● Controlled natural languages, implemented in Prolog:
Attempto Controlled English (ACE), PENG, etc.
● English-like domain-specific languages for legal applications, based on logic programming:Blaux, Oracle Intelligent Advisor
● Syntactic sugar for the logic programming language ASP:PENGASP
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● RegelSpraak?
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Outline of the talk
● The University of Michigan lease termination clause● The British Nationality Act● Rock Paper Scissors Smart Contract*● ISDA (International Swaps and Derivatives) Early Termination● Australian Small Business Rollover*● The default clause of the Flood-Goodenough loan agreement*
*with online implementation in SWISH6
LP logical form
higher-order form
Prolog-like form
style is as important as form
At the beginning, Leibniz develops a general theory of conditions. Later on, he modifies this theory for moral or legal conditions.
According to Leibniz, a condition is a structure consisting of two parts (propositiones partialibus): the “if” part (conditio) and the “then” part (conditionatum).
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The University of Michigan lease termination clause - Allen and Saxon 1984
The University may terminate this lease when the Lessee, having made application and executed this lease in advance of enrolment, is not eligible to enrol or fails to enrol in the University or leaves the University at any time prior to the expiration of this lease, or for violation of any provisions of this lease, or for violation of any University regulations relative to residence or for health reasons, by providing the student with written notice of termination 30 days prior to the effective time of termination, unless life, limb or property would be jeopardised, the Lessee engages in the sale or purchase of controlled substances in violation of Federal, state, or local law, or the Lessee is no longer enrolled as a student, or the Lessee engages in the use of firearms, explosives, inflammable liquids, fireworks or other dangerous weapons within the building or turns in a false alarm in which case a maximum of 24 hours notice would be sufficient.
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The University may terminate this lease when the Lessee,
having made application and executed this lease in advance of enrolment,
is not eligible to enrol or fails to enrol in the University
or leaves the University at any time prior to the expiration of this lease, or for violation of any provisions of this lease, or for violation of any University regulations relative to residence or for health reasons, by providing the student with written notice of termination 30 days prior to the effective time of termination,
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unless life, limb or property would be jeopardised, the Lessee engages in the sale or purchase of controlled substances in violation of Federal, state, or local law,
or the Lessee is no longer enrolled as a student, or the Lessee engages in the use of firearms, explosives, inflammable liquids, fireworks
or other dangerous weapons within the building or turns in a false alarm in which case a maximum of 24 hours notice would be sufficient.
The clause has the ambiguous form:
A if A1 and A2 or A3 or A4 or A5 or A6 or A7unless B1 or B2 or B3 or B4 or B5 in which cases B.
Allen & Saxon (1984) conclude that the intended interpretation is:
((A IF ((A1 AND (A2 OR A3)) OR A4 OR A5 OR A6 OR A7))IF NOT (B1 OR B2 OR B3 OR B4 OR B5))AND (IF (B1 OR B2 OR B3 OR B4 OR B5) THEN B)AND (IF NOT (B1 OR B2 OR B3 OR B4 OR B5) THEN NOT B
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The intended meaning has logic programming form:
((A IF ((A1 AND (A2 OR A3)) OR A4 OR A5 OR A6 OR A7))IF AND NOT (B1 OR B2 OR B3 OR B4 OR B5)).
AND (IF (B1 OR B2 OR B3 OR B4 OR B5) THEN B).AND (IF NOT (B1 OR B2 OR B3 OR B4 OR B5) THEN NOT B
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In Logical English with indentation instead of parentheses
A IF A1
AND A2 OR A3
OR A4 OR A5 OR A6 OR A7
AND NOT B.
BIF B1 OR B2 OR B3 OR B4 OR B5.
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unless B
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Well-written legislation has logic programming form:
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http://demo.logicalcontracts
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with support from and collaboration with
Bruce and Chris Mennell, Aora, LondonAndrew Noble, LodgeIT, Perth
Miguel CalejoBob KowalskiJacinto Dávila
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TaxLog
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An expert system shell midway between Prolog and Logical English
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Example: R&D Tax Reliefs http://demo.logicalcontracts.com:8082/p/research_and_development_tax_reliefs.pl https://www.gov.uk/guidance/corporation-tax-research-and-development-rd-relief
Example: Net Asset Value http://demo.logicalcontracts.com:8082/p/cgt_maximum_net_asset_value.pl
https://www.ato.gov.au/general/capital-gains-tax/small-business-cgt-concessions/basic-conditions-for-the-small-business-cgt-concessions/maximum-net-asset-value-test/
Example: Rollover http://demo.logicalcontracts.com:8082/p/cgt_concessions_sb_restructure_rollover.pl https://www.ato.gov.au/general/capital-gains-tax/small-business-cgt-concessions/small-business-restructure-rollover
Example: Affiliates http://demo.logicalcontracts.com:8082/p/cgt_affiliates.pl
https://www.ato.gov.au/general/capital-gains-tax/small-business-cgt-concessions/basic-conditions-for-the-small-business-cgt-concessions/affiliates/
Example: Reserve Tax reliefs http://demo.logicalcontracts.com:8082/p/stamp_duty_reserve_tax_reliefs.pl https://www.gov.uk/guidance/stamp-duty-reserve-tax-reliefs-and-exemptions
Example: Statutory residence http://demo.logicalcontracts.com:8082/p/statutory_residence_test_guidance.pl
https://www.gov.uk/hmrc-internal-manuals/residence-domicile-and-remittance-basis/rdrm11040 18
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Translates into forall in Prolog.
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2 D2 Legal Technology, London
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ISDA 2002 Master Agreement - Early Termination following Event of Default
6(a) Right to Terminate Following Event of Default. If at any time an Event of Default with respect to a party (the “Defaulting Party”) has occurred and is then continuing, the other party (the “Non-defaulting Party”) may, by not more than 20 days notice to the Defaulting Party specifying the relevant Event of Default, designate a day not earlier than the day such notice is effective as an Early Termination Date in respect of all outstanding Transactions.
If, however, “Automatic Early Termination” is specified in the Schedule as applying to a party, then an Early Termination Date in respect of all outstanding Transactions will occur immediately upon the occurrence with respect to such party of an Event of Default specified in Section 5(a)(vii)(1), (3), (5), (6) or, to the extent analogous thereto, (8),
and as of the time immediately preceding the institution of the relevant proceeding or the presentation of the relevant petition upon the occurrence with respect to such party of an Event of Default specified in Section 5(a)(vii)(4) or, to the extent analogous thereto, (8). 22
It is permitted that a party designates by a notice at a time T2 to an other party that an Early Termination Date in respect of a Transaction occurs at a time T3if the Transaction is outstanding at T3and an Event of Default occurs with respect to the other party at a time T1and the Event of Default is continuing at T2and the notice specifies the Event of Defaultand T2 ≤ T3 and T3-T2 ≤ 20 days
Adds an exception to the rule
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and it is not the case that the Schedule specifies that Automatic Early Termination applies to the other party for the Event of Default.
Higher-order orMetalevel orModal predicates
An event happens at a time T2 if it is permitted that a party designates by an action at a time T1 that the event happens at T2 and the party designates by the action at T1 that the event happens at T2.
T2 could be after T1
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The loan agreement as a Discrete Finite Automaton
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The loan agreement in LPS simulating DFA
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The English formulation of the loan agreement is incoherent.
An event of default occurs retroactively when one of the events (a)-(d) occursif the borrower does not cure the event within two days after the lender notifies the occurrence.
All outstanding payments need to be made immediately (and retroactively)as soon as the Event of Default occurs.
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A more direct representation of the loan agreement in LE, with only events and without states/fluents
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the borrower has an obligation that the borrower pays 550 to the lender on 2015-06-01.
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Lessons learned
● It is hard to design a CNL that is a simple and powerful computer language,is natural to read in English,has very wide coverage.
● Important to have easy-to-use editing, debugging and exploration tools.
● Essential to have a free, easy-to-use online implementation (e.g. on SWISH).
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Prospects for the Future
● All computer languages should be readable without training.● But learning to write will be harder than learning to read.● Learning to write well will be much harder.● We need a corpus of well-written examples.● Legal applications are a good place to start.
Online implementation soon to be available from:http://logicalcontracts.com
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